Maryoo wrote on 2024-07-18, 16:30:

Hello. I recently bought an ASUS P3B-F motherboard which, during startup, shows information to check for an error in the Hardware Monitor in the BIOS. It turned out that the -5V voltage was out of range. I suspect this may be the result of faulty capacitors. I can replace them myself, but I don't know which ones are responsible for the -5V voltage. Could any of you point them out to me on the motherboard? Or maybe it's a completely different fault?

Just update the BIOS for latest version or community patched version from this topic
Modified BIOSes for ASUS P3B-F, P3V4X, P3V133, CUBX, CUBX-E/L and P3C-E

Well, here is the problem because Awardflash hangs after starting and Uniflash does not recognize the Flash ROM chip.

The voltage is likely not supplied by your PSU. Check if your PSU even delivers -5V. If it dates past 2000, chances are low.

You're right! Case solved.

https://youtu.be/9DN3ZYc86Yg?t=169

This is what it looks like with a power supply that has -5V.

Maryoo wrote on 2024-07-18, 16:49:

Well, here is the problem because Awardflash hangs after starting and Uniflash does not recognize the Flash ROM chip.

Flashing the BIOS on an ASUS motherboard should be normally done with AFLASH not AWDFLASH. Also, UniFlash has the -ASUS command line switch in case it doesn't recognize the ROM chip on such motherboard.

Here is a version of Aflash that ought to work: https://theretroweb.com/drivers/190

I just turned off the warning and kept using it with a modern PSU when I was using mine.

The BIOS was successfully updated using Aflash, thank you for your help.

smtkr wrote on 2024-07-18, 22:52:

I just turned off the warning and kept using it with a modern PSU when I was using mine.

Sorry for the thread necromancy - but has this lead to any issues>? I'm having a different issue, only -.02 of -5v and am similarly using a somewhat modern (probably 10-15 years old) PSU. If it's ignorable, I'm very happy to ignore it 🤣.

Image of my voltage monitor in bios: https://imgur.com/a/he0xrzL

Yes you can ignore it if the PSU does not supply -5v. the P3B-f does not need it.

Horun wrote on 2025-08-03, 21:23:

Yes you can ignore it if the PSU does not supply -5v. the P3B-f does not need it.

The board itself does not need it. ISA cards on the board might. In particular some older ISA sound cards need -5V. That's what the -5V line is for: providing one of the voltages needed for the ISA bus. It was removed in ATX 2.x after the ISA bus was deprecated by Intel.

So if you don't use ISA cards, you definitely don't need -5V, but if you do use ISA cards you might. In any event, if you have ISA cards not doing what they should in a system with an ATX 2.x power supply, this is a possible cause to check.

(and yes, I'm sure this is hardly news to you, but maybe is for the person asking the question)

Here is a partial list of cards that require -5v: ISA Cards & Devices Requiring -5V
thought there was a vogons wiki with more info but could not find it 🙁